1. Field of Invention
This invention relates to the field of apparatus and methods for access to, and repair of, underground sewer, water, and other underground pipes; and is more specifically directed to an improved mechanism to provide access to, and to rehabilitate pre-existing access to, such underground pipes, such as an existing manhole.
2. Discussion of Prior Art
Sanitary sewer systems generally include a series of manholes that are connected by sewer pipes to move waste water from sources to a sanitary treatment site. These manholes are most often constructed of concrete or block material and are conventionally shaped of cone, corbel, and bench sections. Typically, the manholes are placed more than a thousand feet apart and are connected by sewer pipes. Conventional manholes are four to five feet in diameter, and each is large enough to admit a maintenance worker into its interior, by design.
The problem with conventional manholes is that they catch water that flows into the manhole from ground level. The water can also flow in from many places, including cracks in the cone and corbel. The cracks are caused by shifts in the surrounding ground, temperature changes that affect the cement, wear from vehicle traffic, and so forth. The blocks or cement of the manholes is also susceptible to disintegration from acids created in sewer systems. Repair is required on a regular basis, and is generally an expensive proposition.
There have been attempts to replace conventional manholes. Reinforced, preformed, plastic casings have been used to replace the concrete manholes. The plastic casings purportedly cost less and eliminate some of the problems found in the concrete manholes. For example, they are less affected by temperature changes, they generally do not crack, and they are impervious to acids in the sewer system. However, current systems have their own problems. For example, the size of some casings makes them expensive to ship, and each casing may not match the requirements of the site terrain where it is to be installed. Additionally, the casings have to be sealed at the bottom to prevent leaks. Moreover, the access can be inconvenient. Maintenance is generally destructive, or at least as expensive as in conventional manholes.
Other attempted replacements have been suggested to overcome problems associated with installing a one-piece, plastic manhole casing. The other suggested casings are segmented in various ways to be assembled and installed at the site. While these casings are less expensive to ship, they are labor intensive at the installation site. They have a single input and output that are of standard size for sewer pipe in line at the sites.
The segmented and slotted casings are prone to leak and may float if installed in an area with a high water table. Most of these preformed casings are constructed of a cone, corbel, and bench in the manner of a concrete manhole. If the casing leaks, water may destroy the complete installation. Unless the casing is securely placed on a concrete foundation and surrounded by a fill material, a high water table can cause it to float and break the connections to input and output sewer pipes.
Consequently, it is not always economical to install a manhole of concrete or preformed plastic into which a maintenance worker can enter. Rather, a less expensive, more easily maintained underground pipe access can be installed to access the underground pipes, which does not necessarily accommodate a human being, but which can accommodate certain maintenance equipment.
Moreover, this apparatus can be removed, so that the conventional manhole remains, thereby permitting access to human maintenance workers. Unlike previous attempts, the removal is non-destructive.
The Port can be made of preformed plastic, polyethylene, fiberglass reinforced resin, or a similar material. It is formed in a shape to be placed below ground inside of a manhole or similar access to underground pipes. It is impervious to acids in the sewer system, and it need not be large enough for a person to enter into its body cavity for maintenance. However, it is large enough to admit equipment into its inner body for maintaining the connecting pipes, that is, equipment to clean out the pipes or admit remote video cameras to inspect the pipes. It is watertight and may have waste water connections that receive water into its inner body from several sources and access the waste water to the sanitary sewer system through an output pipe, just as conventional manholes do. The port is placed below ground and held in position by its own base, which is fixed in the ground. It is not a manhole per se. Rather, it replaces and rehabilitates a manhole by providing an impermeable chamber that is smaller than a conventional manhole, yet the top of which can be removed to access the manhole by maintenance workers in the conventional fashion.
Previous inventions have tried to provide underground pipe access of pre-formed bodies that are smaller than a conventional manhole used in sewer systems, but that can only be removed by destroying them. These purported to be water tight, and available for placement below ground with access to an inner body at ground level. These previous inventions provided only limited non-destructive entry to the inner chamber of the manhole from ground level for maintenance.
The invention resolves a number of problems that previous inventions have not yet addressed.